Converting a fixed jet NOS plate

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sidecar
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Converting a fixed jet NOS plate

Post by sidecar » Tue Jul 30, 2013 7:38 pm

Due to a huge cockup on my part my mate has ended up with a 150bhp nos plate which we were going to fit to his 3.9 lump. We only want to run 50 BHP shot but the plate is not designed to take normal flare jets. I think that I can modify the brass fittings so that a jet can be fitted but one other thing worries me which is the holes in the two tubes. My plate has multiple holes for both the NOS and the fuel, this plate only has four holes in each tube. do you guys think that the plate will be OK? I was actually thinking that less holes 'might' help stop the fuel just dribbling out of the tube and forcing it to be delivered as a spray. This could be wishful thinking on my part!!!



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Re: Converting a fixed jet NOS plate

Post by mgbv8 » Tue Jul 30, 2013 9:46 pm

sidecar wrote:Due to a huge cockup on my part my mate has ended up with a 150bhp nos plate which we were going to fit to his 3.9 lump. We only want to run 50 BHP shot but the plate is not designed to take normal flare jets. I think that I can modify the brass fittings so that a jet can be fitted but one other thing worries me which is the holes in the two tubes. My plate has multiple holes for both the NOS and the fuel, this plate only has four holes in each tube. do you guys think that the plate will be OK? I was actually thinking that less holes 'might' help stop the fuel just dribbling out of the tube and forcing it to be delivered as a spray. This could be wishful thinking on my part!!!



Show us the connections into the plate.
What solenoids is he using?
What fuel pressure is he running?
Is the fuel system a stand alone or is he just nicking fuel from the carb supply?
What is the pipe setup? ie what size and type ?? Is it -4 braided or 4mm nylon.

For such a small hit you would be better off staying away from big lines for nitrous at least. I've got plenty of 4mm nylon fuel and nitrous piping which you can have for nowt.
You just need to buy some fittings to adapt to the smaller nylon lines, and you can buy in line jet holders from wizards of nos. Or you can adapt the solenoid outlets to take wizards jet holders.

The fuel normally just flows out of the bottom holes as a slight squirt from 5psi upwards. The nitrous coming out of the holes at high velocity at 800-900psi in the top bar hits the fuel and drags it into the airstream to mash it up a little.

I use a NOS spray bar plate that I've adapted to 4mm nylon lines.

We need some more info and some pics :)

Perry

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Re: Converting a fixed jet NOS plate

Post by sidecar » Wed Jul 31, 2013 6:28 am

Hi Perry, Thanks for your reply.

I never have any luck posting pictures up on this forum so I’ll just have to describe the setup. :(

Basically we are trying to build a similar setup to my Holley Powershot setup but the main cockup is the NOS plate, it has a brass fitting at either end of the plate which allows the pipes from the solenoids to be connected to the plate, my plate as ali fittings, the problem is that the brass fittings are not designed to take a flare jet, the brass fitting must have the correct size holes in them to ‘hard wired’ the system to be a 150 BHP shot, I can see the restriction so I could drill it out if required but I’d like to keep the drilling to a minimum to avoid swarf getting stuck down the spray bars.

On the fuel side a flare jet does happen to fit into the brass fitting but the pipe that connects the solenoid to the plate is not flared out, it has an olive. On the NOS side the brass fitting will need to be drilled about 1mm deeper in order for a jet to be fitted, again the pipe from the solenoid is wrong as it has an olive. I did see the correct sort of pipes on ebay a while ago but they have sold now. I reckon that I can make a set of pipes from some brass or copper tube and use the nuts that have come with the kit. I’d rather buy a set of ‘plate to solenoid’ pipes but I’ve not any luck in finding them so far.

The kit uses the same solenoids as my kit, they are just generic one’s badged up as Holley Powershot, from memory they can flow 250 BHP’s worth of NOS. The rest of the kit is like my setup, it uses AN4 braided pipe etc. The fuel supply will be at 6.5 PSI and I will just tap into the carb supply but I will check that the pump can deal with the demand.

I use a formula from a book that works well, basically BHP= Fuel Flow in CC per min /4.7 (I’ll then add a generous safety factor) I guess if his engine makes 250 without the NOS with a 50 BHP shot the pump will need to flow 1400cc of fuel per minute and if I add say 400cc to be safe it will need to flow 1800cc/min.

We are only going for a small NOS hit because the ignition system that is fitted has no retard feature, the car is only used on the road not on the strip.

I’m sure that I can get the plate to accept the flare jets, having said that the inline jet holders from WON sound interesting, I’ll check them out but my concern was the lack of holes in the two spray bars.

From your description it sounds like the NOS will still do a good job of ‘smashing’ the fuel up anyway so maybe spray bars with loads of holes are just a marketing gimick?

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Post by sidecar » Wed Jul 31, 2013 5:03 pm

Bit of an update.... I've managed to drill out the brass ends so that I can fit flare jets, also I've found some brake pipe that I can use to make the tubes.

My only worry now is the fact that the spray bars only have 4 holes in them.

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Post by mgbv8 » Wed Jul 31, 2013 7:26 pm

If you look at the size of the hole in a 50hp nos jet and then at the holes in the spray bars you should see that the sums total of the 4 holes is more than the bore size of the jet? The jet will be around 0.7mm or 30 thou?

So no worries for a 50 shot on that plate.

The fittings in the plate will be 1/8th npt or bsp.

You can fit a wizards compression fitting straight in to convert to nylon to avoid all the fuss with solid pipes.

I'm sure the fittings in the solenoids are the same size so these can be replaced with similar fittings that include a jet holder.

On a very small system like this you need to keep pipes as small and as short s possible. Nylon allows you to run with no sharp bends in the system as well so you can have a smooth pipe run from solenoid to plate as short as possible.

Sounds like you have it almost sorted anyway. But dont get sucked into fitting miles of hard pipe, especially copper. Keep the solenoids as close as poss to the plate as well. Keep the bottle to solenoid pipe as short as possible. With AN4 lines you may notice some nitrous lag on the initial hit.

Perry

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Post by sidecar » Thu Aug 01, 2013 8:59 am

Hi Perry,

Thanks for your advice, I will take it on-board, also thanks for the offer of donating some nylon pipe. I reckon that I will be OK with the copper pipe because the ID bore is quite small, maybe 2.5mm. I will keep the runs as short as possible, I think that mine are only 4 inches away so I’ll try to do the same with my mate’s setup. (I run a 110 BHP shot but I still
You are right in that the fittings on the NOS plate are the same thread size as on the solenoids, I will use the olives on the solenoid connection and I’ve managed to flare out the other end of the pipe nicely by spinning it in my lathe then driving into the end of it my ‘live centre’ which was fitted to the lathe tailstock.
The AN4 braided hose is probably a bit large for the shot that we are going to use but I guess it will be Ok-ish. I suppose that because of the small NOS jet which is effectively at the end of the pipe it will take some time to purge the 10ft of AN4 of gas and fill it with liquid NOS so there will be a delay with the ‘hit’

If you reckon that a 4 hole per spray bar will be OK then we will stick with that, I understand your logic and it might in fact produce a better spray from just four holes. Having said that the plate was fixed at a 150 shot so I guess the holes are pretty big.

Cheers,

Pete

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Post by mgbv8 » Thu Aug 01, 2013 7:54 pm

sidecar wrote:Hi Perry,

Thanks for your advice, I will take it on-board, also thanks for the offer of donating some nylon pipe. I reckon that I will be OK with the copper pipe because the ID bore is quite small, maybe 2.5mm. I will keep the runs as short as possible, I think that mine are only 4 inches away so I’ll try to do the same with my mate’s setup. (I run a 110 BHP shot but I still
You are right in that the fittings on the NOS plate are the same thread size as on the solenoids, I will use the olives on the solenoid connection and I’ve managed to flare out the other end of the pipe nicely by spinning it in my lathe then driving into the end of it my ‘live centre’ which was fitted to the lathe tailstock.
The AN4 braided hose is probably a bit large for the shot that we are going to use but I guess it will be Ok-ish. I suppose that because of the small NOS jet which is effectively at the end of the pipe it will take some time to purge the 10ft of AN4 of gas and fill it with liquid NOS so there will be a delay with the ‘hit’

If you reckon that a 4 hole per spray bar will be OK then we will stick with that, I understand your logic and it might in fact produce a better spray from just four holes. Having said that the plate was fixed at a 150 shot so I guess the holes are pretty big.

Cheers,

Pete


Use the 6psi fuel pressure and jet the fuel for a 50 shot. Jet the nitrous for a 25 shot and see how it feels and how the plugs look after a pull. Leave the fuel as is and increase the nitrous as required. To get your 50 shot working on low fuel pressure you may end up with 50 in the nitrous and 75 in the fuel.

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Post by sidecar » Mon Aug 05, 2013 7:28 pm

Hi Perry, (or anyone else who cares to comment!)

I've been thinking!

My NOS hit is not all that hard (100 BHP shot) so I guess my mates 50 BHP shot might feel too soft. So I was looking for some PTFE tube that I could push up the inside of the dash 4 tube that I am running (and the tube my mate will be running). The ID of my tube is 5.35mm and I've found some 4.85mm OD tube which has an ID of 4mm.I know that there will be a very small gap between the two tubes but I was hoping the if I get the length of the inner tube just right the NOS will flow down this tube rather than down the gap between the tubes.

What ya reckon??? :P

Cheers,

Pete

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Post by mgbv8 » Tue Aug 06, 2013 6:42 pm

sidecar wrote:Hi Perry, (or anyone else who cares to comment!)

I've been thinking!

My NOS hit is not all that hard (100 BHP shot) so I guess my mates 50 BHP shot might feel too soft. So I was looking for some PTFE tube that I could push up the inside of the dash 4 tube that I am running (and the tube my mate will be running). The ID of my tube is 5.35mm and I've found some 4.85mm OD tube which has an ID of 4mm.I know that there will be a very small gap between the two tubes but I was hoping the if I get the length of the inner tube just right the NOS will flow down this tube rather than down the gap between the tubes.

What ya reckon??? :P

Pete





If you try to reduce the inner bore of the -4 line like this you are going to create turbulence. And nitrous does not like turbulence.

Lets start again!
Are you going to have the nitrous jet in the solenoid outlet or the plate inlet?
If its going in the plate inlet then leave the -4 as it is. It will act as a fuel log up to the jet as the liquid will back up quite quickly as soon as it hits the restriction of the jet.

You say your 100 shot feels quite tame? What size is the engine and are you using a controller or just a fixed hit?

If the engine sucks up the 100 fixed hit you may not feel much on the road. But on the track or dyno you should see a marked imrpovement.

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Post by JSF55 » Tue Aug 06, 2013 7:22 pm

I tried mine out on the road to make sure it worked, even with a 50 hit on my 3.9 it was very noticable
So thats where it went !

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Post by sidecar » Tue Aug 06, 2013 9:03 pm

Maybe I'm being a bit harsh about my setup, maybe I'm just too used to it. I've ran at least 10 10lbs bottles though it on the road. I can feel the it!

My setup does use the jets in the plate as will the setup for my mate.

My setup is a single hit and I run programmable MSD ignition system which pulls 4 degrees out of the timing when the NOS is running. (0.5 second delay before the timing is pulled out) I know that 4 degrees is quite a lot but my all in figure is quite high for a 4.6 at 32 degrees. The lump runs 10:1 CR and made 285 BHP on the rollers a while ago. Since then I have done a fair bit more to the engine, seat of the pants dyno feels like 300 BHP without the NOS. At the moment I'm running a 49 NOS jet and a 47 fuel jet.

With regards to fitting an inner tube of PTFE I was going to make it a flush fit with the inner bit of the AN fittings at either end of the pipe. I've order the tube now, it was only 20 quid so I might try it, if its no good I can always pull it out!

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Post by mgbv8 » Tue Aug 06, 2013 9:30 pm

sidecar wrote:Maybe I'm being a bit harsh about my setup, maybe I'm just too used to it. I've ran at least 10 10lbs bottles though it on the road. I can feel the it!

My setup does use the jets in the plate as will the setup for my mate.

My setup is a single hit and I run programmable MSD ignition system which pulls 4 degrees out of the timing when the NOS is running. (0.5 second delay before the timing is pulled out) I know that 4 degrees is quite a lot but my all in figure is quite high for a 4.6 at 32 degrees. The lump runs 10:1 CR and made 285 BHP on the rollers a while ago. Since then I have done a fair bit more to the engine, seat of the pants dyno feels like 300 BHP without the NOS. At the moment I'm running a 49 NOS jet and a 47 fuel jet.

With regards to fitting an inner tube of PTFE I was going to make it a flush fit with the inner bit of the AN fittings at either end of the pipe. I've order the tube now, it was only 20 quid so I might try it, if its no good I can always pull it out!

If the jets are in the plate then leave the -4 line as it is mate.

If the 4.6 is only making 285 with nitrous on the dyno then something is wrong?? If this is without nitrous then it aint too bad.

If you want to tune the engine properly you should invest in a wideband AFR kit with logging function. It will save you ££££'s in dyno time as you can log on the fly on track or on a quiet road...

Forget the ptfe liner tube thing. Keep the jet in the plate inlet and you will be fine. Make sure you have enough petrol on tap for the engine + nitrous + at least 25% in hand.

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Post by sidecar » Wed Aug 07, 2013 4:30 am

Thanks for your advice.

It was making 285 without the NOS, I now reckon that it makes 300 without the NOS.

The fuel pump does deliver enough fuel, it is an Edelbrock electric pump, they state that it is good enough for 600 BHP. I've ran the pump into a container then ran the figures though the formula that I posted up earlier.

I also run the car with an Innovate LC1

Cheers,

Pete

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Post by mgbv8 » Wed Aug 07, 2013 9:46 pm

sidecar wrote:Thanks for your advice.

It was making 285 without the NOS, I now reckon that it makes 300 without the NOS.

The fuel pump does deliver enough fuel, it is an Edelbrock electric pump, they state that it is good enough for 600 BHP. I've ran the pump into a container then ran the figures though the formula that I posted up earlier.

I also run the car with an Innovate LC1

Cheers,

Pete

Thats more like it Pete :)

Just a note on doing the fuel pump flow rate checks!!
Most folk do open pipe flow checks into a bucket which doesnt tell you a lot about the pumps ability to overcome the resistance of the system when its in action.

If you have the Edelbrock pump that I think you may have it will have an internal filter + a pressure adjusting screw?

Try adding a restrictor in the fuel pipe into the bucket that simulates the resistance of the needle jets in the carb as well as the jet in the fuel side of the nitrous system and then do the flow check again. This will be a more accurate flow test.

I know it sounds like a lot of fannying around but it can save you a melted engine?

I should know, I've got a good few melted pistons etc on the shelf in the garage :)

I know that you are not running a huge amount of gas but better safe than sorry eh?

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Post by bigaldart » Sun Nov 01, 2015 12:51 am

Rule one with power adders is have enough fuel pump!

Alan

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